Limits of quotients of bivariate real analytic functions

  • Authors:
  • C. Cadavid;S. Molina;J. D. VéLez

  • Affiliations:
  • Universidad EAFIT, Departamento de Ciencias Básicas, Bloque 38, Office 417, Carrera 49 No. 7 Sur-50, Medellín, Colombia;Department of Mathematics, University of Cincinnati, Cincinnati, OH, USA;Universidad Nacional, Medellín, Colombia

  • Venue:
  • Journal of Symbolic Computation
  • Year:
  • 2013

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Abstract

Necessary and sufficient conditions for the existence of limits of the form lim"("x","y")"-"("a","b")f(x,y)/g(x,y) are given, under the hypothesis that f and g are real analytic functions near the point (a,b), and g has an isolated zero at (a,b). The given criterion uses a constructive version of Hensel@?s Lemma which could be implemented in a computer algebra system in the case where f and g are polynomials with rational coefficients, or more generally, with coefficients in a real finite extension of the rationals. A high level description of an algorithm for determining the existence of the limit as well as its computation is provided.